Yellowstone is no ordinary wilderness. Site of the world's first national park, it is a lost world of vast plains and endless forests defended by towering mountains, and home to North America's last great bison herds, the grizzly bear, the wolf. It is also the most extensive thermal area on earth, with more than 10,000 boiling springs, fumaroles and bubbling mud pits, and more geysers than the rest of the world combined. This landmark series reveals the grandeur of this unique place as its animals struggle to survive over the course of its vividly changing seasons.